The hypothesis is that coronary artery lesions with minimal disease will demonstrate a vasoconstrictive response to acetylcholine which will be reduced or absent following cholesterol lowering when restudied 6 months later. The second hypothesis is that the vasoconstrictive response to acetylcholine for lesions of greater hemodynamic significance will not be reduced by cholesterol lowering because of the hemodynamic significance of the lesion which can cause endothelial dysfunction or damage.